I should explain, that cost is for a Stridsberg 16 port MCA216M. It's the only one with 16 ports I have been able to find. Currently I have the ultimate cheap route of using 75ohm coax with two 8-port channelmaster drop amps to keep from losing the signal due to all the splits. It's feels messy and not ideal.
It's 14 scanners and 4 SDR receivers. The goal is to upgrade the antenna to something a little higher quality. Then split that with minimal loss to all the receivers. If there is a cheaper option for a multicoupler with at least 16 ports I am all in favor. For the discone I'm not worried at all about the transmit gain etc since it won't be a factor.
Might make some sense to split things up.
Instead of 16 port multicoupler, use more than one antenna and smaller multicouplers.
Not sure what you are scanning, but it's easy to do better than a discone. If you are scanning multiple bands, a band specific antenna will easily outperform a discone. Add a patch panel, and you'd have some flexibility.
Nothing wrong with using 75Ω stuff. Yeah, there's a very slight impedance mismatch, but you'll find that your scanner and discone are not 50Ω either. A less expensive multicoupler would allow you to spend more money on the antenna system. Getting your antennas up higher and using higher grade coax will make a big difference. RG-11 is low loss….
On the dual band 2m/70c it's just a straight run from radio to antenna with N connectors on both ends. That's what lead me to the X50NA. Has some gain and the right connectors and the bands the radio is in. The run is less then 50 feet and I'm ok with something like LMR400 for that since it's Rx and Tx. From my calculations @ 50feet LMR240 will have about 2-3dB of attenuation but the antenna has about 7dB of gain in the 440 band. Running a calculation at qsl.net gives this result for the LMR-240 specs.
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The loss works both ways, so make sure you consider the receive side of things. If you are not trying to work a lot of simplex, then probably not a big deal and LMR-240 will work just fine. But take a look at the costs, LMR-240 vs. LMR-400, and consider that there's a considerable amount of labor and risk installing them. LMR-240 might be fine, or a higher grade cable may only add a bit of cost.
And I'd not get too hung up on the UHF vs. N connector thing. I saw your post about changing the connector on the back of the radio.
Yeah, N connectors perform better at higher frequencies, but it's really hard to hear that difference on the 440 band. Usually the small additional loss won't be heard. You'd need high end test equipment to see it.
Where the N connectors make a difference is on higher frequencies. The UHF connectors are not true 50Ω, there's a bit of an impedance bump, but you'll not notice that.
Changing out connectors to save a tenth of a dB, but running small coax doesn't seem like a good expenditure of effort in my mind. But, it's a hobby, and if you want to give it a try, go for it and let us know how it works.
There are still a lot of commercial UHF radios that have the SO-239 connectors on the back. It's not really a big deal.